1. Field of the Invention
This invention relates to a device for generating ozonized water by electrolysis of water and a method for generating ozonized water with this device, and more particularly an ozonized water generating device and a method for generating ozonized water with this device in which an inner side of a casing is defined into an anode chamber and a cathode chamber by a solid electrolyte film, an anode electrode attached noble metal having an ozone generating catalyst function is arranged at the solid electrolyte film surface at the anode chamber and a cathode electrode is arranged at the solid electrolyte film surface at the cathode chamber, respectively.
2. Discussion of the Background
Although both a gas dissolving method and a water electrolysis method have been well known as a typical method for obtaining ozonized water in the prior art, it is worthy of notice to apply a water electrolysis method in recent years which has some advantages such as a small-sized device, applicability of water which may easily be available as raw material and sufficient application of small-sized power source device of several tens volts and several tens amperes.
As a device applied in an efficient generating method for generating ozone by the aforesaid water electrolysis method, such devices as those disclosed in Japanese Patent Laid-Open Nos. Hei 1-312092, 8-134677 and 8-134678, for example. A schematic configuration of this device is made as shown in FIG. 13 that an inside part of the casing 81 is divided into the anode chamber 83 and the cathode chamber 84 by the solid electrolyte film 82, the anode electrode 86 made of noble metal (platinum or the like) 85 with an ozone generating catalyst function is contacted with the solid electrolyte film surface at the anode chamber side and the cathode electrode 88 made of noble metal (platinum, silver and the like) 87 is contacted with the solid electrolyte film surface at the cathode chamber side, respectively, each of the anode chamber 83 and the cathode chamber 84 is provided with raw water flow inlets 89, 90 and electrolized water flow outlet ports 91, 92 and further a DC power source 93 is connected between the anode electrode 86 and the cathode electrode 88.
In the case of the ozonized water generating device with the configuration shown in FIG. 13, when a DC current is flowed between both electrodes 86, 88, an electrolysis of water is produced between the noble metallic catalyst 85 for the anode and the noble metallic catalyst 87 for the cathode with the solid electrolyte film 82 being held between them, both oxygen and ozone are generated at the anode electrode 86 and hydrogen is generated at the cathode electrode 88, respectively, and ozone generated at the anode side is dissolved in water to attain ozonized water. To attain the ozonized water of high concentration in an efficient manner by this ozonized water generating device, one of the present applicants has proposed it in the Japanese Patent Laid-Open No. 8-134677. Its content shows that the noble metal (platinum or the like) 85 having an ozone generating catalyst function is formed into a metallic net shape and the anode electrode 86 having a configuration in which a lath net made of anti-corrosion metal is laminated at catalyst side surface. In the case of this anode electrode 86, the raw water being supplied to the anode chamber 83 is restricted to flow in a flow passage formed by the metallic net and the lath net, so that the water becomes a severe turbulence flow to generate an eddy flow while flowing through the metallic net and the lath net, ozone generated at the anode side is dissolved instantaneously after generation of ozone in the raw water becoming the severe turbulence flow and at the same time its action is accumulated continuously while the water is flowing at the anode electrode surface, resulting in that the ozonized water of high concentration can be generated in view of two effects of an instantaneous dissolution and the accumulating actions.
However, even such an ozonized water generating device shows that if a continuous operation is performed to attain a predetermined ozone concentration under an initial set current density, a deterioration of performance of the film itself is promoted and it becomes hard to maintain an ozone concentration as a time elapses, resulting in that a current density must be increased only by an amount corresponding to a reduced concentration of ozone. As understood from FIG. 14 showing a relation between the ozone concentration and the current density, a continuous operation to increase the current density causes the current density to reach an upper limit value in a current density variable region which is a limit value of the ozonized water generating device (time t1), subsequent to the upper limit value of the current density, there occurs a reduction of the ozone concentration and lastly the ozone concentration is lower than an allowable value, resulting in that the stop operation (time t2) occurs. Then, to return the device from this state to its initial performance state, the ozonized water generating device is decomposed to replace the solid electrolyte film itself, resulting in that the decomposing of the device and the replacing work for the electrolyte are quite troublesome and take such time, a life of the solid electrolyte film is short and an efficiency of use of the solid electrolyte film in regard to the generating of ozonized water is kept low.
This invention has been invented to eliminate the above problems and its object is to study a cause of deterioration of performance of the solid electrolyte film itself and extend a life of the solid electrolyte film and at the same time to provide an ozonized water generating device capable of reducing a frequent decomposition of the device as well as a frequent replacement of the solid electrolyte film and a rational method for generating ozonized water under application of this device.
The present inventors have met the above problems, surveyed and studied a surface state of the solid electrolyte film after its replacement to check a cause of deterioration of performance of the solid electrolyte film. However, the present inventors have used again the solid electrolyte film by chance while a clear cause can not be found, and found that the film can be used under a state in which the film substantially keeps its initial performance. After this state, the present inventors tried to use again a solid electrolyte film left for more than a certain period of time after replacement of the solid electrolyte film and found that the film can be used sufficiently. As described above, although a reason why the solid electrolyte film is recovered in its performance is not clear at present, a reason found in the prior art ozonized water generating device is assumed to be considered that the electrodes are always impressed against the solid electrolyte film with a resilient member or the like placed between the electrodes and the casing, a certain distortion may occur at holes of the film where hydrogen ions may pass from the anode side toward the cathode side under application of the impressing force and the electrolysis action to cause the hydrogen ions to be hardly passed through the holes, and the distortion is recovered after the solid electrolyte film is removed and left for more than a specified period of time. In addition, in the case that the impressing surface of each of the electrodes is a surface as found in a metallic net, in particular, the impressing position on the solid electrolyte film surface is changed when the film is used again, so that it may be considered that the recovering is promoted by this fact.
Its subsequent survey and study clarified that when the impressing force of the electrodes against the solid electrolyte film is increased after the current density reached up to the upper limit value in the current density variable region of a limit value of the ozonized water generating device, ozonized water with a predetermined concentration under a lower current density can be produced, and accordingly a generating of ozonized water can be continued until the current density reaches again up to the upper limit value in the current density variable region. A reason why this state occurred is assumed to be considered that although the solid electrolyte film surface having been contacted with the electrodes up to now was deteriorated and reached up to the upper limit value of current density, a new abutting surface with the electrodes, i.e. a region where the electrolysis can be applied was increased due to increasing the impressing force of the electrodes against the solid electrolyte film and a performance of electrolysis was recovered, thereby it is possible to assure an electrolysis time of longer hours than that of the prior art and then it becomes possible to extend a life of the solid electrolysis film.
However, even if the solid electrolyte film can be used again or used in its extended time as described above, the electrodes in the prior art ozonized water generating device were impressed against the solid electrolyte film by a resilient member or the like arranged between each of the electrodes and the casing in order to reduce a resistance between the solid electrolyte film and each of the electrodes and perform an efficient production of ozone and the solid electrolyte film which could not keep a performance of electrolysis had to be still replaced with a new one after decomposing the device.
In reference to the foregoing, it is an object of the present invention to provide a device capable of performing a long term stable and efficient generating of ozonized water and more particularly a device in which the solid electrolyte film can be used continuously for a long period of time.
The present invention has been invented in view of the aforesaid features, and it is characterized in that an inside of a casing is defined by a solid electrolyte film into an anode chamber and a cathode chamber, an anode electrode attached noble metal having an ozone generating catalyst function is arranged to be impressed against the solid electrolyte film at the anode chamber, a cathode electrode is arranged to be impressed against the solid electrolyte film at the cathode chamber, respectively, each of said anode chamber and said cathode chamber is formed with a raw water flow inlet port and an electrolized water flow outlet port, and a DC voltage is applied between said anode electrode and said cathode electrode, wherein either one of or both said anode electrode and said cathode electrode are arranged in such a way that they can be impressed against or removed from said solid electrolyte film by an movable driving means. With such an arrangement as above, the present invention is constituted such that the impressing force of either one or both of said anode electrode and said cathode electrode against said solid electrolyte film can be changed or both the impressing and the removing can be repeated.
In addition, as the first method for generating ozonized water with the ozonized water generating device of the present invention, there is provided a method for generating ozonized water in which an anode electrode made of noble metal having an ozone generating catalyst function is arranged at one surface of a solid electrolyte film, a cathode electrode is arranged at the other surface of said solid electrolyte film, at least one of both electrodes can be attached to or detached from said solid electrolyte film, a DC voltage is applied between said electrodes while raw water is flowing at each of the electrodes, wherein the ozonized water is generated under the state in which at least one of said electrodes is being impressed against said solid electrolyte film with a predetermined impressing force, a concentration of ozone in said generated ozonized water is detected and a current density of said DC current is changed in response to a variation of said concentration of ozone in such a way that said concentration of ozone may become substantially constant. As its modified examples of this method, there are a method in which said current density is increased before the ozone concentration in said generated ozonized water becomes less than a predetermined value and an impressing force of said electrodes against the solid electrolyte film is increased as said current density reaches a predetermined upper limit value; a method in which applying of said DC voltage is stopped before an ozone concentration of said produced ozonized water becomes less than a predetermined concentration, an impressing force of said electrodes against the solid electrolyte film is released, a DC voltage is applied again after elapsing a predetermined period of time, said electrodes are impressed against said solid electrolyte film and generating of ozonized water is re-started; and a method in which an operation for increasing said current density before an ozone concentration in said produced ozonized water becomes less than a predetermined concentration and increasing an impressing force of said electrodes against the solid electrolyte film as said current density reaches a predetermined upper limit value is carried out more than at least once, thereafter said applying of DC voltage is stopped before said ozone concentration becomes less than a predetermined concentration, releasing the impressing force of said electrodes against said solid electrolyte film, applying a DC voltage again after elapsing a predetermined period of time, impressing said electrodes against said solid electrolyte film and re-starting generating of ozonized water.
In addition, as the second method, there is provided a method for generating ozonized water characterized in that a predetermined DC current value is electrically applied between said electrodes under the state of said at least one electrodes being impressed against said solid electrolyte film, an ozone concentration of the generated ozonized water is detected and an impressing force of said electrodes against the solid electrolyte film is changed in response to a variation of said ozone concentration so as to cause said ozone concentration to be kept substantially constant. This second method has some modified examples as follows. That is, there are provided a method in which an impressing force of said electrodes against the solid electrolyte film is increased before the ozone concentration in said produced ozonized water becomes less than a predetermined value and said current density is increased when said impressing force reaches a predetermined upper limit value; or a method in which applying of said DC voltage is stopped before the ozone concentration of said generated ozonized water becomes less than a predetermined concentration, the impressing force of said electrodes against said solid electrolyte film is released, a DC voltage is applied again after elapsing a predetermined period of time, said electrodes are impressed against said solid electrolyte film to re-start generating of the ozonized water; and a method in which after an operation for increasing an impressing force of said electrodes against the solid electrolyte film before the ozone concentration of said generated ozonized water becomes less than a predetermined concentration and increasing said current density when said impressing force reaches a predetermined upper limit value is carried out more than at least once, applying of said DC voltage is stopped before said ozone concentration becomes less than a predetermined ozone concentration, the impressing force of said electrodes against said solid electrolyte film is released, the DC voltage is applied again after elapsing the predetermined period of time, said electrodes are impressed against said solid electrolyte film to re-start generating of ozonized water.
In all these methods, an impressing force of either one of or both the anode electrode and the cathode electrode in respect to the solid electrolyte film is changed to cause a new impressing surface to be generated and the solid electrolyte film to be activated, resulting in that a continuous electrolysis time can be substantially extended and a film life itself can be extended. Concurrently, it is possible to reduce the number of times of decomposing the ozonized water generating device to replace the solid electrolyte film, resulting in that a maintenance of the device may also be facilitated.
In addition, whatever any of these methods may be applied for generating ozonized water, a continuous generating of ozonized water becomes possible under a state in which a plurality of ozonized water generating devices are installed, said plurality of ozonized water generating devices are changed over in operation to generate ozonized water in a continuous manner in such a way that an ozonized water generating state is produced at least one unit of ozonized water generating device under the state in which the applying of said DC voltage is stopped in at least one unit of ozonized water generating device and an impressing of said electrodes against the solid electrolyte film is released.